Header <regex> is finally working (probably) in gcc-4.9.

Add better tests for it as well.

include/boost/config/stdlib/libstdcpp3.hpp

@@ -162,6 +162,11 @@
 // Note that although <atomic> existed prior to gcc 4.8 it was largely unimplemented for many types:
 #  define BOOST_NO_CXX11_HDR_ATOMIC
 #endif
+#if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 9) || !defined(__GXX_EXPERIMENTAL_CXX0X__)
+// Although <regex> is present and compilable against, the actual implementation is not functional
+// even for the simplest patterns such as "\d" or "[0-9]". This is the case at least in gcc up to 4.8, inclusively.
+#  define BOOST_NO_CXX11_HDR_REGEX
+#endif
 //  C++0x headers not yet (fully!) implemented
 //
 #  define BOOST_NO_CXX11_HDR_THREAD
@@ -169,8 +174,5 @@
 #  define BOOST_NO_CXX11_HDR_CODECVT
 #  define BOOST_NO_CXX11_ATOMIC_SMART_PTR
 #  define BOOST_NO_CXX11_STD_ALIGN
-// Although <regex> is present and compilable against, the actual implementation is not functional
-// even for the simplest patterns such as "\d" or "[0-9]". This is the case at least in gcc up to 4.8, inclusively.
-#  define BOOST_NO_CXX11_HDR_REGEX
 
 //  --- end ---

test/boost_no_cxx11_hdr_regex.ipp

@@ -18,7 +18,12 @@ int test()
 {
   using std::regex;
   using std::wregex;
-  return 0;
+
+  regex e("\\d+");
+  wregex we(L"\\s+");
+  std::string s("123456");
+  std::wstring ws(L"123456");
+  return regex_match(s, e) && regex_match(ws, we) ? 0 : 1;
 }
 
 }